Corrosion preventing agent



2,783,203 conRosroN PREVENTING AGENT John P. McDermott, Springfield, N.J., assignor to Ess-o Research and Engineering Company, a corporation ofDelaware No Drawing. Application May 18, 1955, Serial No. 509,409

9 Claims. (Cl. 252,46.6)

The present invention relates to the improvement of hydrocarbon productsderived from petroleum sources and more particularly to the preparationof improved mineral lubricating oil compositions by-the incorporationtherein of a new class of additives which impart improved properties tosuch hydrocarbon products.

This application is a continuation-in-part of Serial No. 192,617, filedon October 27, 1950 and now abandoned.

in the development of petroleum lubricating oils the trend has been touse more and more eflicient refining methods in order to reduce thetendency of the oils to form carbon and deposits of solid matter orsludge. While such highly refined oils possess many advantages, theirresistance to oxidation, particularly under conditions of severeservice, is generally decreased and they are more prone to form solubleacidic oxidation products which are corrosive. They are generally lesseffective than the untreated oils in protecting the metal surfaces whichthey contact against rusting and corrosion due to oxygen and moisture.Although generally superior to lightly refined oils they may depositfilms of varnis on hot metal surfaces,-such as the pistons of internalcombustion engines, under very severe engine operating conditions.

In accordance with the present invention a new class of compounds hasbeen discovered which when added to refined lubricating oils in smallproportions substantially reduce the tendency of such oils'to corrodemetal surfaces, and which are particularly eflective in inhibiting thecorrosion of copper-lead and cadmium-silver bearings. They are likewiseeffective in inhibiting oxidation of such oils and other petroleumhydrocarbon products, as will be more fully explained hereinafter.

The new class of materials which have been found to possess theantioxidant and stabilizing qualities described above are oil-solublereaction products of organo-substituted dithiophosphoric acids andstyrene oxide. Such products may be defined broadly by the formula:

where R is an aliphatic, cycloaliphatic or aliphatic-aromatic organicradical, preferably a hydrocarbon radical, and where one of the symbolsR1, R2, R3, and R4 represents aiphenyl radical and the others of thesymbols R1, R2, R3 and R4 represent hydrogen atoms. Two dif ferent Rradicals maybe present in the product. It is to be understood that theradicals represented by R in the above formula may also containsubstituents such as halogen atoms or nitro groups. In general, thenumber of carbon atoms in the R radicals should be sufiicient to form aproduct having good oil solubility. Oil solubilizing radicals of about 3to 30 carbon atoms are preferred. When R is an aliphatic hydrocarbonradical, it is preferred that it be an alkyl radical containing about 3to 18 carbon atoms, particularly abut3 to-S carbon States Paten atoms;when R is an aliphatic-aromatic hydrocarbon radical, it is preferredthat it be an alkyl phenyl radical containing about 4 to 18 carbonatoms, particularly 6 to 12 carbon atoms, in the alkyl group; and when Ris a cycloaliphatic hydrocarbon radical, it is preferred that it be analkyl cyclohexyl radical containing about 1 to 4 carbon atoms in thealkyl group. The preferred compounds are those where R is an aliphaticradical of relatively short chain length, preferably as stated above, analkyl group containing about 3 to 8 carbon atoms.

' The following typical examples are representative of thedithiophosphoric acids which may be reacted with styrene oxide inaccordance with the present invention:

Diisopropyl dithiophosphoric acid Di-n-butyl dithiophosphoric acidDiisobutyl dithiophosphoric acid Di-n-octyl dithiophosphoric acidDi-tert.-octyl dithiophosphoric acid Di-(ethylhexyl) dithiophosphoricacid Dinonyl dithiophosphoric acid Di-(Cs oXo) dithiophosphoric acidDioleyl dithiophosphoric acid Dilauryl dithiophosphoric acidDi-(methylcyclohexyl) dithiophosphoric acid Di-(isopropylcyclohexyl)dithiophosphoric acid Di-(tert.-octylphenyl) dithiophosphoric acidDi-(2,4,6-triisobutylphenyl) dithiophosphoric acid The above listeddithiophosphoric acids may be prepared by reacting an alcohol or phenolwith phosphorus pentasulfide by means well known in the art, and it isto be understood that the invention applies not only to simple acids butto mixtures of acids formed by reacting phosphorus pentasulfide withmixtures of alcohols, such, for example as the mixtures of C10 to C18aliphatic alcohols known as Lorol alcohols, and the mixture of alcoholsderived by the oxidation of paraffin wax. Included also are productsderived from the mixture of branched chain aliphatic alcohols obtainedin the 0x0 process.

The reaction between the dithiophosphoric acid and styrene oxide is aspontaneous exothermic reaction which takes place immediately uponcontact of the reactants at normal room temperatures, and may beconveniently conducted by adding about one mole of the styrene oxideslowly to one mole of the dithiophosphoric acid while rapidly stirringthe reaction mixture and controlling the temperature by means of a wateror ice bath. General- 1y temperatures in the range of about 20 to C.

may be employed. No catalyst is required, and the time required for thecompletion of the reaction is not greater than two hours and is usuallymuch less. Reaction times of about 0.2 to 2 hours may generally beemployed. Solvents are not normally required, but in some cases it maybe convenient to conduct the reaction in the presence of well knowninert solvents such as ethylene dichloride, benzene, xylene, or amineral oil.

The amount of the additives of the present invention which is to beemployed in mineral lubricating oil compositions or other petroleumhydrocarbon compositions (which generally will contain a majorproportion of the petroleum hydrocarbonoil) will normally range fromabout 0.02% to 5%, more generally from about 0.1 to about 2% by weightbased on the total composition, and the particular amount in individualcases will be selected in accordance with the requirements of the caseand in view of the properties of the base stock employed. For commercialpurposes, it is convenient to prepare concentrated oil solutions in'which the amount of additive in the composition ranges from 25 to 50% byweight, and to transport and store them in such form. In preparing alubricating oil composition for use as a crankcase lubricant theadditive concentrate is merely blended with the base oil in the requiredamount.

The preparation and testing of the additives of the present inventionare illustrated in the examples described below, but it is to beunderstood that the additives prepared and tested are illustrative onlyand are not to be construed as limiting the scope of the invention inany manner.

Example l.-Diisopropyl dithiophosphorz'c acid-styrene oxide reactionproduct A mixture of 120 g. (2 mols) of isopropanol and 111 g. (0.5 mol)of P255 was heated at 95 C. for 45 minutes in a H. 3-necked flaskequipped with a stirrer, thermometer and reflux condenser. The product(diisopropyl dithiophosphoric acid) was then filtered to remove a smallamount of unreacted P285, after which the filtrate was blown withnitrogen for 30 minutes on the steam bath.

The acid was then transferred to a 4-necked, 1-l. flask equipped with astirrer, thermometer, reflux condenser and dropping funnel. 120 g. ofstyrene oxide (1 mol) was then added over a period of 1 hour, keepingthe temperature under 45 C. by means of a cold water bath. The reactionmixture was then stirred at room temperature for 1 hour. A pale yellowliquid was obtained which upon analysis was found to contain 8.7%phosphorus and 16.6% sulfur.

Example 2.Di-(methylcyclohexyl) dithiophosphoric acid-styrene oxidereaction product A mixture of 228 g. (2 mols) of methylcyclohexanol and111 g. (0.5 mol) of P285 was heated at 105 C. for 1 hour. The product,di-(methylcyclohexyl) dithiophosphoric acid, was then filtered to removea small amount of unreacted P285, after which the filtrate was blownwith nitrogen for 20 minutes on the steam bath.

With rapid stirring, 120 g. (1 mol) of styrene oxide was added dropwiseover a period of one hour keeping the temperature under 50 C. by meansof a cold water bath. The reaction mixture was then stirred at roomtemperature for 1 hour followed by nitrogen blowing for 30 minutes. Aviscous dark liquid was obtained which analyzed 5.4% phosphorus and12.2% sulfur.

Example 3.Di-(nonylphenol) dithiophosphoric acidstyrene oxide reactionproduct A mixture of 440 g. (2 mols) of nonylphenol and 111 g.

(0.5 mol) of PzSs was heated at 150 C. for 1.5 hours. After cooling toroom temperature, the viscous product was dissolved in an equal volumeof carbon tetrachloride r Example 4.-S. O. D. Corrosion Test Blends wereprepared containing 0.25% by weight of each of the products of Examples1 to 3 in a paraffinic mineral lubricating oil of SAE 20 grade.

These blends and a sample of the unblended base oil were submitted to acorrosion test, known as the S. O. D.

Corrosion Test, designed to measure the effectiveness of the product ininhibiting the corrosiveness of a typical mineral lubricating oil towardthe surfaces of copper-lead bearings. The test was conducted as follows:500 cc. of the oils was placed in a glass oxidation tube (13 inches longand 2% inches in diameter) fitted at the bottom with a A inch air inlettube perforated to facilitate air distribution. The oxidation tube wasthen immersed in a heating bath so that the oil temperature wasmaintained at 325 F. during the test. Two quarter sections of automotivebearings of copper-lead alloy of known weight having a total area of 25sq. cm. were attached to opposite sides of a stainless steel rod whichwas then immersed in the test oil and rotated at 600 R. P. M., thusproviding sufficient agitation of the sample during the test. Air wasthen blown through the oil at the rate of 2 cu. ft. per hour. At the endof each 4-hour period the bearings were removed, washed with naphtha andweighed to determine the amount of loss by corrosion. The bearings werethen repolished (to increase the severity of the test), reweighed, andthen subjected to the test for additional 4-hour periods in like manner.The results are given in the following table as corrosion life, whichindicates the number of hours required for the bearings to lose mg. inweight, determined by interpolation of the data obtained in the variousperiods.

Oil or oil blend Bearing corrosion life (hrs) The products of thepresent invention may be employed not only in ordinary hydrocarbonlubricating oils but also in the heavy duty type of lubricating oilswhich have been compounded with such detergent type additives as metalsoaps, metal petroleum sulfonates, metal phenates, metal alcoholates,metal alkyl phenol sulfides, metal organo phosphates, phosphites,thiophosphates, and thiophosphites, metal xanthates and thioxanthates,metal thiocarbamates, and the like. Other types of additives, such asphenols and phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of thisinvention may be straight mineral lubricating oils or distillatesderived from paraflinic, naphthenic, asphaltic or mixed base crudes, or,if desired, various blended oils may be employed as well as residuals,particularly those from which asphaltic constituents have been carefullyremoved. The oils may be refined by conventional methods using acid,alkali and/or clay or other agents such as aluminum chloride, or theymay be extracted oils produced by solvent extraction with solvents suchas phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may beemployed as well as synthetic oils, prepared, for example, by thepolymerization of olefins or by the reaction of oxides of carbon withhydrogen or by the hydrogenation of coal or its products, or by theesterification of dicarboxylic acids with alcohols and/or glycols.

For the best results the base stock chosen should normally be an oilwhich with the new additive present gives the optimum performance in theservice contemplated. However, since one advantage of the additives isthat their use also makes feasible the employment of less satisfactorymineral oils, no strict rule can be laid down for the choice of the basestock. The additives are normally sulficiently soluble in the basestock, but in some cases auxiliary solvent agents may be used. Thelubricating oils will usually range from about 40 to seconds (Saybolt)viscosity at 210 F. The viscosity index may range from 0 to 100 or evenhigher.

Other agents than those which have been mentioned may be present in theoil composition, such as dyes, pour point depressants, heat thickenedfatty oils, sulfurized fatty oils, sludge dispersers, antioxidants,thickeners, viscosity index improvers, oiliness agents, resins, rubber,olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers anddefoamers are the higher alcohols having preferably 8-20 carbon atoms,e. g., octyl alcohol, lauryl alcohol, stearyl. alcohol, and the like.

In addition to being employed in lubricants, the additives of thepresent invention may also be used in other petroleum oil products suchas motor fuels, heating oils, hydraulic fluids, torque converter fluids,cutting oils, flushing oils, turbine oils, transformer oils, industrialoils, process oils, and the like, and generally as antioxidants inmineral oil products. They may also be used in gear lubricants, greasesand other products containing mineral oils as ingredients.

What is claimed is:

l. A petroleum hydrocarbon product containing dissolved therein acorrosion inhibiting amount of an oilsoluble compound of theformulawhere R is an organic radical selected from the group consistingof aliphatic, cycloaliphatic and aliphatic-aromatic organic radicals;and Where one of the symbols R1, R2, R3, and R1 represents a phenylradical and the others of the symbols R1, R2, R3 and R4 representhydrogen atoms.

2. A composition according to claim 1 in which the petroleum hydrocarbonproduct is a lubricating oil fractron.

3. A composition according to claim 1 in which R represents ahydrocarbon radical.

4. A composition according to claim 1 in which R is an alkyl groupcontaining 3 to 8 carbon atoms.

5. A composition according to claim 1 in which R represents amethyl-cyclohexyl radical.

6. A composition according to claim 1 in which R represents an isopropylradical.

7. A composition according to claim 1 in which R represents a nonylphenyl radical.

8. A lubricating oil composition comprising a major proportion of amineral lubricating oil and in the range of about 0.02 to 5% by weight,based on the total composition, of an oil-soluble compound of theformula where R is an organic radical selected from the group consistingof aliphatic, cycloaliphatic and aliphatic-aromatic organic radicals;and where one of the symbols R1, R2, R3, and R4 represents a phenylradical and the others of the symbols R1, R2, R3 and R1 representhydrogen atoms.

9. A composition consisting essentially of a mineral lubricating oil andabout 25 to by weight of an oilsoluble compound of the formulawhere R isan organic radical selected from the group consisting of aliphatic,cycloaliphatic and aliphatic-aromatic organic radicals; and where one ofthe symbols R1, R2, R3, and R1 represents a phenyl radical and theothers of the symbols R1, R2, R3 and R4 represent hydrogen atoms.

References Cited in the file of this patent UNITED STATES PATENTS2,531,129 Hook et a1. Nov. 21, 1950

1. A PETROLEUM HYDROCARBON PRODUCT CONTAINING DISSOLVED THEREIN ACORROSION INHIBITING AMOUNT OF AN OILSOLUBLE COMPOUND OF THE FORMULA-